The objective of this proposal is to extend our understanding of the reovirus type 3 receptor (Reo3R): a complex known to bind to a discrete surface of the reovirus type 3 hemagglutinin (HA3) and to be involved in neural cell differentiation and function. The receptor has been biochemically isolated and found to be composed of two subunits: a 35-65 kD glycosylated protein (CD147) and a 95 kD protein. The 95 kD subunit is a complex of CD147 associated with a multiple membrane-spanning monocarboxylate transporter receptor. Further biological and biochemical studies will be undertaken to examine the use of CD147 as a receptor for reovirus type 3 (T3D) in vivo. Detailed characterization of the biochemistry and features of pathogenesis resulting from binding of T3D to this receptor will be undertaken. Our previous efforts to study receptor signaling focused on the characterization of two structures that bind to this receptor complex. These structures are HA3 and the low affinity monoclonal anti-receptor antibody MAb 87.92.6, particularly one of its complementarity-determining regions from the light chain. We have defined many of the molecular and biological consequences of these interactions. In this proposal, we will focus on the molecular analysis of the reovirus receptor, signal transduction through the receptor, as well as its role in the pathogenesis of neural infection of newborn mice with T3D. We will employ a new set of reagents, including polyclonal and monoclonal antibodies, for this analysis. These reagents bind with high affinity to the Reo3R and block T3D attachment and subsequent infection. In addition, we will continue our efforts to determine the biological role the Reo3R plays in development of neural cells. We will continue to define the receptor's function in the developing optic nervous system and its special role in MuIler and ganglion cells of the retina and in the pineal gland using the high affinity MAb species. We will study two types of transgenic animals: the CD147-/- mouse and a transgenic created by using the interphotoreceptor binding protein (IRBP) promoter coupled with the MAb light chain that recognizes the Reo3R, 87.92.6L. The pineal gland and some retinal cells are genetically ablated in rodents expressing IRBP-87.92.6L. We will study T3D neural pathogenesis in these mutant mice and also define principles of the role of the Reo3R complex in affecting pineal and retinal nerve development.